Mold or matrix for plating



Sept. 6, 1932. LAUKEL 1,875,346

' MOLD OR MATRIX FOR PLATING Filed May 13, 1926 gwmntoz 172%02" Zak!Patented Sept. 6, 1932 UNITED STATES ARTHUR K. LAUKEL, OF DETROIT,MICHIGAN MOLD B MATRIX FOB PLATING Application filed Kay 18,

This invention relates to the production or preparation of molds,matrices or molded bodies, for electrodeposition, such for example as inthe making of electrodeposited met- '5' al patterns according to PatentNo. 1,570,634 granted to me on the 26th day of January,

One of the outstanding features of an electrodeposited pattern is thatit may be 0 made in true duplication of another pattern, there being noshrinkage in the electrodeposited pattern to be provided for and nonecessity for machining and finishing as in ordinary molded metalpatterns to prolduce precise dimensions or fineness of finish,

but to insure such true duplication of a pattern it is necessarythat theimpression in the mold shall be a true counterpart of the pattern to beduplicated. It will be obvious that if a mold be made with such trueimpression and thereafter the impression coated with a medium of anyappreciable thicliness to produce a conductive surface so that it may beplated, such medium would alter the dimensions or contour of the impression to a degree depending upon the thickness thereof and a resultmgelectrodeposited pattern would suffer distortion to such extent.

The plating of molds having deep relief, such as in the production ofelectrodeposited patterns, involves peculiar roblems or conditionsrequiring more particular consideration than ordinary electroplatingprocesses such for instance as the production of electrotypes whereinpulverized graphite is often used .to produce a conductive surface, andother electroplating processes well known to those conversant with theart wherein powdered metal suspended in lacquer is often used toprovidea conducting surface, and it is found that in plating molds having deeprelief in which the molds are often suspended for long periods in theelectrolyte before a complete flashing or initial plating in the deeperrecesses, and in which accuracy is to be maintained as hereinbeforestated, that such methods of providing a conductive surface are notsuitable. Pow- 0 ders, such as graphite, do not always adimmediatelysurrounding the pattern. After 1928. Serial 1T0. 108,715.

here sufficiently to the surface of the mold, are diflicult to apply tointricate and extensive surfaces in a manner ensuring an even coat, arediflicult to apply to deep depressions such as often occur in molds formechanical patterns; and lacquer may be de ficient in conducting qualitydue to separation of metallic grains by the vehicle or surfaceinsulation of the grains by such vehicle as well as altering the contourof the mold due to the thickness of the coating of lacquer as beforestated.

It is also desirable that the conductive coating on the mold be porous,which is not always the case with lacquers, and that the deposit shalltend to adhere to the coatin in contradistinction to the effect securedWhere graphite is used.

' Further objects subsidiary to or resulting from the aforesaid objectsor from the construction or operation of the invention as it may becarried into effect will become apparent as the said invention ishereinafter further disclosed. a

In carrying the said invention into effect I may arrange a pattern to beduplicated on a suitable board or plate upon which is placed a framesurrounding the pattern to determine the size of the mold to be made. Ithen coat this patternrwith a mixture of copper dust plaster of Parisand water having the consistency of a heavy paint. Care is taken to makethis coating thorough and also to spread the coating on the surface ofthe plate this coating has set sufliciently to prevent its beinginadvertently erased from the surface of the pattern the frame may befilled with plastic material such as plaster of Paris which will adhereto the aforesaid coating so that the two will become to all intents andpurposes integral. The resultant mold being removed from the patternwhen it has set sufiiciently to warrant such removal. The impression ofthe pattern in the resulting mold and the immediately surroundingsurface of the mold then have a surface in which is imbedded copperdust, and I treat this surface with silver nitrate which produces asilver surface of a conductive nature suitable for subsequent platingoperations. To prevent deleterious action of the electrolyte on thematerial from which the mold is formed, I impregnate the mold with waxin any suitable manner such as by immersing for a sufficient length oftime in a hot bath of wax, after which the surface of the impression andthe surface of the mold contiguous thereto are cleaned of wax by meansof a suitable solvent such as ether. The silvering may be effectedbefore or after the waxing operation or both before and after the waxingoperation, and silver nitrate may be used in combination with the waxsolvent in order to effect this silvering when the wax is removed. If,as on large molds the wax leaves a clean surface due to its absorptionby the material of the mold, such cleaning is not necessary.

All of which is more particularly described and ascertained hereinafter,by way of example, having reference to the accompanying drawing, whereinFigure 1 indicates in plan a pattern mounted upon a board upon wh ch aframe is arranged, the said pattern being shown as partly coated withthecomposition used in producing the conducting surface of the mold to bemade;

Figure 2 is a vertical section of the same illustrating the completecoating applied;

Figure 3 is a similar view to Figure 2, illustrating the framesubsequently filled with plastic material;

Figure 4 illustrates in section a completed mold, and

Figure 5 is a face view of the same.

Similar characters of reference indicate similar parts in the severalfigures of the drawing.

1 indicates a pattern board upon which is mounted a pattern 2 intendedto be reproduced by electrodeposition, and 3 is a frame arranged on theboard around the pattern to form a box-like structure, in which the moldmay be prepared. It is presumed that the surface of the pattern andpattern board are of such nature that the materials used in themanufacture of the mold will not adhere thereto, otherwise such surfacesmay be oiled or treated in any material suitable to pre- Vent suchadherence.

The first step in producing the mold is to prepare a mixture of plasterof Paris or similar suitable material and copper with sufiicient waterto provide a heavy paint-like composition, and for this purpose I havefound that these ingredients may be in the proportions of 112 grammes ofcopper dust, 168 grammes of plaster of Paris, and about 200 c. c. ofwater. In order to get the best'results in such composition the coppershould be of that nature which has a tendency to be wetted by water, andI prefer to use dust of a fineness which will pass through three hundredmesh screen. I

y the pattern board as indicated by the'reference numeral 5, taking carethat all the corners and depressions in the pattern are effectivelyfilled. After this coating has set lsufiiciently that it will not bebroken or eroded from the pattern when other material is poured into theframe, I,fi1l the frame with plastic material such as plaster of Paris6, to form the body of the mold. This material in setting adheres to andbecomes practically integral with the coating already applied to thepattern so that the mold so formed is characterized by the impression 7of the pattern having a surface layer densely filled with smallparticles of copper, the same being true of the surface of the moldimmediately surrounding said impression.

These copper particles are not in such close association, however, thatthey will form a good conducting surface, and in orderto secure suchgood conducting surface I treat the exposed copper particles with asolution containing a metal electro negative to the copper such as asolution of silver nitrate, whereupon the said surface is silvered andthe effect of such silvering is to produce a practically continuoussilver surface which is an excellent conductor and eminently suitablefor the purposes.

The copper is embedded in the surface mixture, and since at least a partof this copper is comprised in the conductive coating, it may be saidthat this coating is partially embedded or anchored in the surface. Theparticles of metal which are deposited in the subsequent process ofelectro-plating adhere firmly to the conductive coating. The firmadherence of the conductive coating to the plaster and of the depositedmetal to the coating constitutes such a great resistance to lifting bygas bubbles resulting from the action of the electrolyte on the plasterof Paris, that this gas pressure, acting by bubbles, is insuflicient tolift the coating or the deposited metal from the plaster. Consequentlythe deposit remains undistorted by gas bubbles, and such gas escapes byminute division of the bubbles and penetration of these divisionsthrough the deposit which is porous in its early stages.

Plaster of Paris in the form in which it is most convenientlv securedcontains about one percent of calcium carbonate which the acid in anelectrolyte, such as copper sulphate electrolyte, will ordinarily attackand decompose with the evolution of carbon dioxide,.and in the making ofpatterns by electrodeposition the evolution of such gas is objectionableas it is liable to accumulate under the deposited metal and therebydistort it. Moreover, unprotected plaster of Paris would be quicklydisintegrated by the action of such anelectrolyte, so that it isnecessary that the mold be suitably treated to enable it to resist thedeleterious action of the electrolyte.

This protection of the mold against the action of the electrolyte may beaccomplished by impregnating the mold withv wax, and the resultingcoating of wax may be afterwards removed from the surface of theimpression in the mold and the immediately surrounding surface of theface of the mold by means of a solvent such as ether if the wax hasnotbeen absorbed by the mold to such an extent as to render thisunnecessary.

Th silvering process already referred to may be carried out eitherbefore or after the waxing process, or both before and after the waxingprocess, as it may be repeated as often as desired to secure aneffective silvering of the surface, and, if thought necessary ordesirable the silver nitrate may be in solution with the alcohol andether so that the removal of the wax surface and the silvering may beeffected to all intents and purposes in one operation.

The incorporating of the copper dust in the coating at the surfaces ofthe mold 'to be plated also reduces the percentage of carbonate contentin such coating, incidently reducing the tendency of the electrolyte toevolve gas on the surface to be plated. There is always liable to be acertain amount of such gas produced, however, where plaster of Paris isused, and it is a feature of the describedmethod of producing aconducting surface that such surface is more or less porous and allowssuch gas to freely escape during the flashing, or early stages ofplating, as distinguished from the trapping of such gases which wouldresult were such surface coated with a substantially non-porous lacquer,and thus the raising or distorting of the flashing which might otherwiseoccur'during the early stages of the plating operation, is avoided.

Furthermore, theiilvering process doesnot reduce the dimensions ofthe imression of the pattern as it would be reduce by the application of acoating of lacquer or other conducting film of appreciable thickness tothe surface of the impression so that the true form of the pattern to beduplicated is fullymaintained.

Such conductive surface will not wash off in the electrolyte, and therealso is the peculiarity that deposited metal tends to adhere closelythereto instead of to detach itself therefrom as is the case wheregraphite is used. This adherence also tends to prevent the depositedfilm from leavin the mold under influence of gas from the mo (1.

It will be realized that although copper dust is described as beingutilized in the coating applied to the pattern in the manufacture of themold other materials may be effectively used, and that other .mediumsmay be'employed for producing the final conductive surface, forinstance, zinc dust may be used and theconductive surface attained bytreating with a cadmium salt solution or platinum solution, tin dustmay-be used and treated with a, solution of silver or copper, or

lead dust may be used and treated with a solution of silver, mercury orcopper, and so forth.

The ingredient incorporated in the coat ing for the production of theconducting surface need not necessarily be a metal. For instance,cadmium oxide and ,cadmium suboxide may-be mixed with plaster of Parisand subsequently treated with a solution of nitrate of silver to producea metallic silver surface or silver chloride may be mixed with plasterof Paris andsubsequently treated with potassium iodide to produce aconducting surface of silver iodide and such variations may be madethrough the chemical range of ingredients suitable for the production ofa conducting surface in the manner related.

The nature ofthe metal forming-the conducting surface must of course besuited to the electrolyte in which the mold is to be plated;

It will be also understood that although plaster of Paris is referred toherein as being very convenient and practical material for use in themanufacture of molds in accordance with this invention, other moldablematerials, as for example wax, having characteristics lending themselvesto manipulation in the manner described and use in a plating bath, maybe utilized.

It will be further understood that although the invention has beendescribed more especially in connection with molds for use in the makingof electrodeposited metal patterns of a mechanical nature, theincorporating of a material adapted to enter into the eventualproduction of a conductive surface on an article to be plated in. the.material forming the surface of the article to be plated is capable of avery wide range of application. Thus ornamental or other objects to beplated may have their entire surface coating prepared in the mannerdescribed or in fact the entire object to be plated may be made of aplastic material with which is admixed copper dust or such ingredient,the article being afterwards treated with the re quired solution tosecure the conducting surface inthe manner hereinbefore explained.Therefore it is to be understood that expressions such as surfacecoating used herein and in the claims are not intended to indicate thatthe coating referred to shall be necessarily restricted to thesurfacelayer of the article as the article to be plated may becompletely formed of the composition hearing the copper dust or suchingredient, in which case of course the surface of the article wouldstill have the properties and be of the nature ascribed thereto.

Still further it should be noted that the second stage in the process oftreating the article may consist in the actual plating thereof insteadof a treatment of the surface of the article in the manner describedprior to such plating. For instance, the article to be plated may havecopper dust incorporated in its surface and be then plated in a silverbath, in which case the initial effect would he a flashing similar tothat secured by the previously described treatment with the solution ofthe silver salt, the only difference being that the plating is continueduntil a required thickness of deposit such as may be called for in thefinished article is secured.

The invention also is not limited to treatment by a metallic salt inorder to secure a conductive coating, as the surface of the article mayhave incorporated therein any suitable substance which is adapted toenter into a reaction with any other agent, which may as a result ofsuch reaction, form a conductive coating on the article in the mannerrequired. Thus silver or copper dust may be incorporated in the surfaceof the article which may then be subjected to the action of a gas suchas hydrogen sulphide, thereby resulting in the formation on the surfaceof the article of copper or silver sulphide as the case may be, which isof a conductive nature. Then again, silver may be incorporated in the Asurface of the article and treated with a solution of iodine in anorganic solvent such as carbon disulphide, thereby forming a coating onthe surface of the article of silver iodide which is also of aconductive nature.

From the various examples which have been given, it will be understoodthat the material incorporated in the surface of the article may in somecases be metallic and in others non-metallic, and the reagent used maybe of a metallic or non-metallic nature according to the chemicalrequirements necessary to obtain the result desired, and the essence ofthe invention therefore lies in the incorporation in the surface of thearticle to be plated of a substance lending itself to treatment by asuitable reagent which will as a result of such reaction, form aconductive surface on the article. Consequently, although the reagentmay be characterized by its containing a metal electro-negative to thematerial incorporated in the surface of the article, this need notalways be the case, as generally speaking the reagent may be said to bereducible by the incorporated material in the surface of the articlewhether this be the result of electrolytic or of chemical action.

This invention may be developed within the scope of the following claimswithout departing from the essential features of the said invention, andit is desired that the specification and drawing be read as merelyillustrative and not in a limiting sense, except as necessitated by theprior art.

What I claim is 1. The method of preparing a molded counterpart of amodel for electroplating which consists in applying to the model acoating of plastic material having incorporated therein a substancewhich when treated with the salt of a metal reducible by it will resultin a conductive coating of such metal being formed on the surfacetreated, subsequently backing said coating with a body of plasticmaterial adapted to adhere to said coating, removing the resulting moldafter setting from the model, and treating the exposed surface of thecoating with such metallic salt.

2. The method of preparing an article for electroplating which consistsin making a body of the article of a mixture of plaster of Paris andmetallic dust, and treating the surface of the article with the salt ofa metal electro-negative to said metalic dust.v

3. The method of preparing an article for electroplating, which consistsin making a body of plaster of Paris containing carbonate, reducing thepercentage of carbonate content in the surface of the article byincorporating in the plaster of Paris a substance of lower carbonatecontent than plaster of Paris and which when treated with the salt of ametal reducible by it will result in a conductive coating of such metalformed on the surface treated, and treating the surface of the articlewith such salt.

4. The method of preparing an article for electroplating, in order toreproduce an object by electro-deposition, consisting in applying tosaid object a plaster of Paris mixture of such low carbonate content asto evolve a negligible quantity of carbon dioxide when immersed in anacid bath, backing said material for reinforcement, separating thearticle thus formed from said object, and rendering the impressedsurface of said material conductive.

5. The method of preparing a cathode for reproduction of an article byelectro-deposi tion, wherein the cathode-carrying body consists mainlyof a material containing carbonate, said method consisting'in applyingover said article a substance of lower carbonate content than saidmaterial, backing said substance with said body material, and renderingthe impressed or molded surface of said substance conductive.

6. The method of preparing a cathode for reproducing an object byelectro-deposition, consisting in selecting two substances capable ofreacting with each other to form a conductor, mixing one of saidsubstances with a material adapted to set without substantialshrinkage,applying said mixture in substantial thickness over saidobject, backing said1 mixture with another material adapted to adherefirmly to said mixture, removing the whole, after setting, from saidobject, and treating the impressed surface of said mixture with theother selected substance.

7. The method of preparing a cathode for reproducing an objectbyelectro-deposition, consisting in selecting two substances capable ofreacting with each other to form a conductor, mixing one of saidsubstances with a material adapted to set without substantial shrinkageand adapted to become porous to carbon dioxide when set, applying saidmixture in substantial thickness over said object, backing said mixturewith another material adapted to adhere firmly to said mixture, removingthe whole, after setting, from said object, and treating the impressedsurface of said mixture with the other selected substance.

8. The method of reproducing a surface by electro-deposition consistingin applying to said surface a plastic mixture containing a reagentincorporated therein, reinforcing said material, removing said materialand reinforcement, from said surface after hardening, intact from saidsurface, treating the impressed surface thereof with a reagent capableof reacting with the first reagent to form an electrically conductivesurface, depositing metal electrolytically on said conductive surface,and separating the deposit from said conductive surface.

9. The method of reproducing a surface by electro-deposition consistingin applying to said surface a plastic mixture containing a reagentincorporated therein, said mixture bein' adapted to set withoutsubstantial shrin age, reinforcing said material, re moving saidmaterial and reinforcement from said surface after hardening, intactfrom said surface, treating the impressed surface thereof with a reagentcapableiof reacting with the first reagent to form an electricallyconductive surface, depositing metal electrolytically on said conductivesurface, and separating the deposit from said conductive surface.

10. The method of reproducing a surface by electro-deposition consistingin applying .to said surface a plastic mixture containing a reagentincorporated therein, said material being adapted to set withoutsubstantial shrinkage and being porous when set,

chemically united with said particles.

In testimony whereof I aflix my signature.

' ARTHUR K. LAUKEL.

reinforcing said material, removing said material and reinforcement,after hardening, intact from said surface, treating the impressedsurface thereof with a reagent caable of reacting with the first reagentto orm an electrically conductive surface, de-

